Contoured fluid-filled chamber

ABSTRACT

A fluid-filled chamber may be incorporated into footwear and other products. The chamber is formed from a polymer material that defines a first surface, a second surface located opposite the first surface, and a sidewall surface extending around a periphery of the chamber and between the first surface and the second surface. A plurality of bonds are spaced inward from the sidewall surface and join the first surface and the second surface, and the bonds are distributed to form a regularly-spaced array, such as a hexagonal array. In some configurations, the first surface and the second surface may define elliptically-shaped structures between the bonds. In addition, the bonds may be formed to have a slope that is an average of slopes of the first surface and the second surface in areas proximal the bonds.

BACKGROUND OF THE INVENTION

A conventional article of athletic footwear includes two primaryelements, an upper and a sole structure. The upper may be formed from aplurality of material elements (e.g., textiles, leather, and foammaterials) that define a void to securely receive and position a footwith respect to the sole structure. The sole structure is secured to alower surface of the upper and is generally positioned to extend betweenthe foot and the ground. In addition to attenuating ground reactionforces, the sole structure may provide traction and control various footmotions, such as pronation. Accordingly, the upper and the solestructure operate cooperatively to provide a comfortable structure thatis suited for a wide variety of ambulatory activities, such as walkingand running.

The sole structure of an article of athletic footwear generally exhibitsa layered configuration that includes a comfort-enhancing insole, aresilient midsole at least partially formed from a polymer foammaterial, and a ground-contacting outsole that provides bothabrasion-resistance and traction. Suitable polymer foam materials forthe midsole include ethylvinylacetate or polyurethane that compressesresiliently under an applied load to attenuate ground reaction forces.Conventional polymer foam materials compress resiliently, in part, dueto the inclusion of a plurality of open or closed cells that define aninner volume substantially displaced by gas. Following repeatedcompressions, the cell structure of the polymer foam may deteriorate,thereby resulting in decreased compressibility and decreased forceattenuation characteristics of the sole structure.

One manner of reducing the mass of a polymer foam midsole and decreasingthe effects of deterioration following repeated compressions is toincorporate a fluid-filled chamber into the midsole. In general, thefluid-filled chambers are formed from an elastomeric polymer materialthat is sealed and pressurized. The chambers are then encapsulated inthe polymer foam of the midsole such that the combination of the chamberand the encapsulating polymer foam functions as the midsole. In someconfigurations, textile or foam tensile members may be located withinthe chamber or reinforcing structures may be bonded to an exteriorsurface of the chamber to impart shape to or retain an intended shape ofthe chamber.

Fluid-filled chambers suitable for footwear applications may bemanufactured by a two-film technique, in which two separate sheets ofelastomeric film are formed to exhibit the overall peripheral shape ofthe chamber. The sheets are then bonded together along their respectiveperipheries to form a sealed structure, and the sheets are also bondedtogether at predetermined interior areas to give the chamber a desiredconfiguration. That is, interior bonds (i.e., bonds spaced inward fromthe periphery) provide the chamber with a predetermined shape and sizeupon pressurization. In order to pressurize the chamber, a nozzle orneedle connected to a fluid pressure source is inserted into a fillinlet formed in the chamber. Following pressurization of the chamber,the fill inlet is sealed and the nozzle is removed. A similar procedure,referred to as thermoforming, may also be utilized, in which a heatedmold forms or otherwise shapes the sheets of elastomeric film during themanufacturing process.

Chambers may also be manufactured by a blow-molding technique, wherein amolten or otherwise softened elastomeric material in the shape of a tubeis placed in a mold having the desired overall shape and configurationof the chamber. The mold has an opening at one location through whichpressurized air is provided. The pressurized air induces the liquefiedelastomeric material to conform to the shape of the inner surfaces ofthe mold. The elastomeric material then cools, thereby forming a chamberwith the desired shape and configuration. As with the two-filmtechnique, a nozzle or needle connected to a fluid pressure source isinserted into a fill inlet formed in the chamber in order to pressurizethe chamber. Following pressurization of the chamber, the fill inlet issealed and the nozzle is removed.

SUMMARY OF THE INVENTION

One aspect of the invention is a fluid-filled chamber that may beincorporated into footwear and other products. The chamber is formedfrom a polymer material that defines a first surface, a second surfacelocated opposite the first surface, and a sidewall surface extendingaround a periphery of the chamber and between the first surface and thesecond surface. A plurality of bonds are spaced inward from the sidewallsurface and join the first surface and the second surface, and the bondsare distributed to form a regularly-spaced array, such as a hexagonalarray. In some configurations, the first surface and the second surfacemay define elliptically-shaped structures between the bonds.

Another aspect of the invention is a method of manufacturing afluid-filled chamber. The method includes locating a first sheet and asecond sheet of a polymer material between a pair of mold portions. Thefirst sheet and the second sheet are compressed together between themold portions to form (a) a peripheral bond that joins the first sheetand the second sheet around a periphery of the chamber and (b) aplurality of interior bonds that join the first sheet and the secondsheet and are spaced inward from the peripheral bond. In someconfigurations, the interior bonds may be located to form aregularly-spaced array. In addition, the chamber may be sealed toenclose a fluid within the chamber and between the first sheet and thesecond sheet.

The advantages and features of novelty characterizing aspects of theinvention are pointed out with particularity in the appended claims. Togain an improved understanding of the advantages and features ofnovelty, however, reference may be made to the following descriptivematter and accompanying drawings that describe and illustrate variousembodiments and concepts related to the invention.

DESCRIPTION OF THE DRAWINGS

The foregoing Summary of the Invention and the following DetailedDescription of the Invention will be better understood when read inconjunction with the accompanying drawings.

FIG. 1 is a lateral side elevational view of an article of footwearincorporating a fluid-filled chamber.

FIG. 2 is a medial side elevational view of the article of footwearincorporating the chamber.

FIG. 3 is a perspective view of the chamber.

FIG. 4 is a top plan view of the chamber.

FIGS. 5A-5D are a cross-sectional views of the chamber, as defined bysection lines 5A-5D in FIG. 4.

FIG. 6 is a bottom plan view of the chamber.

FIG. 7 is a lateral side elevational view of the chamber.

FIG. 8 is a medial side elevational view of the chamber.

FIG. 9 is a perspective depicting an alternate configuration of thechamber.

FIG. 10 is a top plan view of the alternate configuration of thechamber.

FIGS. 11A-11C are schematic cross-sectional views, as defined by sectionline 11-11 in FIG. 10 and illustrating a method of designing a structureof the chamber.

FIG. 12 is a perspective view of a mold for forming the chamber.

FIGS. 13A-13C are side elevational views of the mold depicting steps ina manufacturing process of the chamber.

FIG. 14 is a perspective view of the chamber and residual portions ofpolymer sheets forming the chamber following the manufacturing process.

FIGS. 15A-15E are top plan views of alternate configurations of thechamber.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion and accompanying figures disclose variousconfigurations of fluid-filled chambers suitable for use in solestructures of articles of footwear. Concepts related to the chambers andthe sole structures are disclosed with reference to footwear having aconfiguration that is suitable for running. The chambers are not limitedto footwear designed for running, however, and may be utilized with awide range of athletic footwear styles, including basketball shoes,tennis shoes, football shoes, cross-training shoes, walking shoes, andsoccer shoes, for example. The chambers may also be utilized withfootwear styles that are generally considered to be non-athletic,including dress shoes, loafers, sandals, and boots. An individualskilled in the relevant art will appreciate, therefore, that theconcepts disclosed herein apply to a wide variety of footwear styles, inaddition to the specific style discussed in the following material anddepicted in the accompanying figures. In addition to footwear, conceptsassociated with the fluid-filled chambers may also be applied to avariety of other consumer products.

Footwear Structure

An article of footwear 10 is depicted in FIGS. 1 and 2 as including anupper 20 and a sole structure 30. For reference purposes, footwear 10may be divided into three general regions: a forefoot region 11, amidfoot region 12, and a heel region 13, as shown in FIGS. 1 and 2.Footwear 10 also includes a lateral side 14 and a medial side 15.Forefoot region 11 generally includes portions of footwear 10corresponding with the toes and the joints connecting the metatarsalswith the phalanges. Midfoot region 12 generally includes portions offootwear 10 corresponding with the arch area of the foot, and heelregion 13 corresponds with rear portions of the foot, including thecalcaneus bone. Lateral side 14 and medial side 15 extend through eachof regions 11-13 and correspond with opposite sides of footwear 10.Regions 11-13 and sides 14-15 are not intended to demarcate preciseareas of footwear 10. Rather, regions 11-13 and sides 14-15 are intendedto represent general areas of footwear 10 to aid in the followingdiscussion. In addition to footwear 10, regions 11-13 and sides 14-15may also be applied to upper 20, sole structure 30, and individualelements thereof.

Upper 20 is depicted as having a substantially conventionalconfiguration incorporating a plurality material elements (e.g.,textiles, foam, leather, and synthetic leather) that are stitched oradhesively bonded together to form an interior void for securely andcomfortably receiving a foot. The material elements may be selected andlocated with respect to upper 20 in order to selectively impartproperties of durability, air-permeability, wear-resistance,flexibility, and comfort, for example. An ankle opening 21 in heelregion 13 provides access to the interior void. In addition, upper 20may include a lace 22 that is utilized in a conventional manner tomodify the dimensions of the interior void, thereby securing the footwithin the interior void and facilitating entry and removal of the footfrom the interior void. Lace 22 may extend through apertures in upper20, and a tongue portion of upper 20 may extend between the interiorvoid and lace 22. Given that various aspects of the present applicationprimarily relate to sole structure 30, upper 20 may exhibit the generalconfiguration discussed above or the general configuration ofpractically any other conventional or non-conventional upper.Accordingly, the structure of upper 20 may vary significantly within thescope of the present invention.

Sole structure 30 is secured to upper 20 and has a configuration thatextends between upper 20 and the ground. The primary elements of solestructure 30 are a midsole 31 and an outsole 32. Midsole 31 may beformed from a polymer foam material, such as polyurethane orethylvinylacetate, that encapsulates a fluid-filled chamber 40 toenhance the ground reaction force attenuation characteristics of solestructure 30. In addition to the polymer foam material and chamber 40,midsole 31 may incorporate one or more plates, moderators, orreinforcing structures, for example, that further enhance the groundreaction force attenuation characteristics of sole structure 30 or theperformance properties of footwear 10. Outsole 32, which may be absentin some configurations of footwear 10, is secured to a lower surface ofmidsole 31 and may be formed from a rubber material that provides adurable and wear-resistant surface for engaging the ground. Outsole 32may also be textured to enhance the traction (i.e., friction) propertiesbetween footwear 10 and the ground. In addition, sole structure 30 mayincorporate an insole or sockliner (not depicted) that is located within the void in upper 20 and adjacent a plantar (i.e., lower) surface ofthe foot to enhance the comfort of footwear 10.

Chamber Configuration

Chamber 40 is depicted individually in FIGS. 3-8 as having aconfiguration that is suitable for footwear applications. Whenincorporated into footwear 10, chamber 40 has a shape that fits within aperimeter of midsole 31 and substantially extends from forefoot region11 to heel region 13 and also from lateral side 14 to medial side 15,thereby corresponding with a general outline of the foot. When the footis located within upper 20, chamber 40 extends under substantially allof the foot in order to attenuate ground reaction forces that aregenerated when sole structure 30 is compressed between the foot and theground during various ambulatory activities, such as running andwalking.

An exterior of chamber 40 is formed from a polymer material thatprovides a sealed barrier for enclosing a pressurized fluid. The polymermaterial defines an upper surface 41, an opposite lower surface 42, anda sidewall surface 43 that extends around a periphery of chamber 40 andbetween surfaces 41 and 42. As discussed in greater detail below,chamber 40 may be formed from a pair of polymer sheets that are moldedand bonded during a thermoforming process to define surfaces 41-43. Moreparticularly, the thermoforming process (a) imparts shape to one of thepolymer sheets in order to form upper surface 41 and an upper portion ofsidewall surface 43 (b) imparts shape to the other of the polymer sheetsin order to form lower surface 42 and a lower portion of sidewallsurface 43, (c) forms a peripheral bond 44 that joins a periphery of thepolymer sheets and extends around sidewall surface 43, and (d) forms aplurality of interior bonds 45 that join interior portions of thepolymer sheets and extends between surfaces 41 and 42. Whereasperipheral bond 44 joins the polymer sheets to form a seal that preventsthe fluid from escaping, interior bonds 45 prevent chamber 40 fromexpanding outward or otherwise distending due to the pressure of thefluid. That is, interior bonds 45 effectively limit the expansion ofchamber 40 to retain a contoured shape of surfaces 41 and 42.

Chamber 40 is shaped and contoured to provide a structure that issuitable for footwear applications. As noted above, chamber 40 has ashape that fits within a perimeter of midsole 31 and extends undersubstantially all of the foot, thereby corresponding with a generaloutline of the foot. In addition, surfaces 41 and 42 are contoured in amanner that is suitable for footwear applications. With reference toFIGS. 7 and 8, chamber 40 exhibits a tapered configuration between heelregion 13 and forefoot region 11. That is, the portion of chamber 40 inheel region 13 exhibits a greater overall thickness than the portion ofchamber 40 in forefoot region 11. Chamber 40 also has a configurationwherein the portion of chamber 40 in heel region 13 is generally at agreater elevation than the portion of chamber 40 in forefoot region 11.More particularly, the portion of upper surface 41 in heel region 13 israised above the portion of upper surface 41 in forefoot region 11, andthe portion of lower surface 42 in heel region 13 is raised above theportion of lower surface 42 in forefoot region 11. The tapering ofchamber 40 and the differences in elevations in areas of upper surface41 impart an overall contour to chamber 40 that complements the generalanatomical structure of the foot. That is, these contours ensure thatthe heel of the foot is slightly raised in relation to the forefoot.

In addition to tapering and changes in elevation between regions 11 and13, upper surface 41 is contoured to provide support for the foot.Whereas lower surface 42 is generally planar between sides 14 and 15,upper surface 41 forms a depression in heel region 13 for receiving theheel of the foot, as depicted in FIG. 5A. That is, the heel of the footmay rest within the depression to assist with securing the position ofthe foot relative to chamber 40. Upper surface 41 may also protrudeupward in the portion of midfoot region 12 corresponding with medialside 15 in order to support the arch of the foot, as depicted in FIG.5B. In addition, upper surface 41 has a generally planar configurationin forefoot region 11 for supporting forward portions of the foot, asdepicted in FIG. 5C. Accordingly, upper surface 41 defines variouscontours to further complement the general anatomical structure of thefoot.

Interior bonds 45 are regularly-spaced from each other and arranged toform a hexagonal array. That is, many of interior bonds 45 aresurrounded by six other interior bonds 45 that form a hexagonal shape.As discussed in greater detail below, however, interior bonds 45 may bearranged in a triangular array, a square array, a rectangular array, orin an irregular distribution. Interior bonds 45 may also be arranged inan array that includes a combination of different arrays (e.g., acombination of hexagonal and triangular arrays). Depending upon variousfactors that include the overall dimensions of chamber 40, the thicknessof chamber 40, and the pressure of the fluid within chamber 40, forexample, the distance between adjacent interior bonds 45 may vary fromtwo to thirty millimeters or more. Depending upon similar factors, thediameter of each interior bond may be five millimeters, but may alsorange from two to ten millimeters or more. Although interior bonds 45are depicted as being circular, other shapes may be utilized.

FIGS. 5A-5D depict various cross-sections through chamber 40 andillustrate the configuration of upper surface 41 and lower surface 42between adjacent interior bonds 45. In heel region 13, the polymermaterial of surfaces 41 and 42 cooperatively form twoelliptically-shaped structures between each of the adjacent interiorbonds 45 in heel region 13, as depicted in FIG. 5A. Two additionalelliptically-shaped structures are also formed between sidewall surface43 and interior bonds 45 that are adjacent to sidewall surface 43. Eachof the four elliptically-shaped structures are oriented such that a longaxis extends vertically, whereas a short axis extends between theadjacent interior bonds 45 or between sidewall surface 43 and interiorbonds 45. In midfoot region 12, the polymer material of surfaces 41 and42 cooperatively form five elliptically-shaped structures that are alsooriented such that a long axis extends vertically, as depicted in FIG.5B. In comparison with the elliptically-shaped structures in heel region13, however, the elliptically-shaped structures in midfoot region 12 aresomewhat less eccentric. That is, the elliptically-shaped structures inheel region 13 have a greater height to width ratio than theelliptically-shaped structures in midfoot region 12. In forefoot region11, the polymer material of surfaces 41 and 42 cooperatively form fiveelliptically-shaped structures that are effectively circular in shape,as depicted in FIG. 5C. In comparison with the elliptically-shapedstructures in midfoot region 12 and heel region 13, therefore, theelliptically-shaped structures in forefoot region 11 are less eccentric.

The differences in eccentricity between the elliptically-shapedstructures of regions 11-13 relates to the differences in verticalthickness of chamber 40 in regions 11-13. Given that the spacing betweenadjacent interior bonds 45 is the same for each of regions 11-13, thewidth of each of the elliptically-shaped structures in regions 11-13 issubstantially constant. Given that the vertical thickness of chamber 40is different in each of regions 11-13, however, the length or verticalheight of each of the elliptically-shaped structures changes betweenregions 11-13. More particularly, the elliptically-shaped structuresexhibit greater eccentricity in areas of chamber 40 with greaterthickness, and the elliptically-shaped structures exhibit lessereccentricity in areas of chamber 40 with lesser thickness.

When the fluid within chamber 40 is pressurized, the fluid places anoutward force upon the polymer material forming surfaces 41 and 42.Although the shape of chamber 40 does not change significantly betweenthe pressurized and unpressurized states, the outward force of the fluidexpands or otherwise distends chamber 40 to a relatively small degree.One attribute of chamber 40 that contributes to the relatively smalldegree of expansion or distension is the presence of theelliptically-shaped structures between adjacent interior bonds 45. Thatis, the elliptically-shaped structures provide a relatively stableconfiguration that resists deformation to a greater degree than someother shapes. Moreover, elliptically-shaped structures with a height towidth ratio equal to or greater than one (i.e., the vertical height isgreater than or equal to the width) are more stable in chamber 40 thanelliptically-shaped structures with a height to width ratio less thanone (i.e., the vertical height is less than the width). Referring to thecross-sections of FIGS. 5A-5C, each of the elliptically-shapedstructures exhibit a height to width ratio equal to or greater than one.Accordingly, the elliptically-shaped structures in chamber 40 arerelatively stable.

As noted above, one factor that is relevant to determining a properdistance between adjacent interior bonds 45 is the thickness of chamber40. When the thickness of chamber 40 is greater than or equal to thedistance between edges of adjacent interior bonds 45, theelliptically-shaped structures exhibit a height to width ratio equal toor greater than one. As discussed above, the thickness of chamber 40 isgreater than or equal to the distance between edges of adjacent interiorbonds 45 in a majority of chamber 40 to impart greater height thanthickness to a majority of the elliptically-shaped structures, therebyforming the elliptically-shaped structures to be relatively stable whenchamber 40 is pressurized with the fluid. If, however, the thickness ofchamber 40 is less than the distance between edges of adjacent interiorbonds 45, the elliptically-shaped structures may exhibit a height towidth ratio less than one. In some configurations of chamber 40, amajority or all of the elliptically-shaped structures may exhibit aheight to width ratio less than one.

The polymer material forming the exterior or outer barrier of chamber 40encloses a fluid pressurized between zero and three-hundred-fiftykilopascals (i.e., approximately fifty-one pounds per square inch) ormore. In addition to air and nitrogen, the fluid contained by chamber 40may include octafluorapropane or be any of the gasses disclosed in U.S.Pat. No. 4,340,626 to Rudy, such as hexafluoroethane and sulfurhexafluoride, for example. In some configurations, chamber 40 mayincorporate a valve that permits the individual to adjust the pressureof the fluid.

A wide range of polymer materials may be utilized for chamber 40. Inselecting materials for the outer barrier of chamber 40, engineeringproperties of the material (e.g., tensile strength, stretch properties,fatigue characteristics, dynamic modulus, and loss tangent) as well asthe ability of the material to prevent the diffusion of the fluidcontained by chamber 40 may be considered. When formed of thermoplasticurethane, for example, the outer barrier of chamber 40 may have athickness of approximately 1.0 millimeter, but the thickness may rangefrom 0.25 to 2.0 millimeters or more, for example. In addition tothermoplastic urethane, examples of polymer materials that may besuitable for chamber 40 include polyurethane, polyester, polyesterpolyurethane, and polyether polyurethane. Chamber 40 may also be formedfrom a material that includes alternating layers of thermoplasticpolyurethane and ethylene-vinyl alcohol copolymer, as disclosed in U.S.Pat. Nos. 5,713,141 and 5,952,065 to Mitchell, et al. A variation uponthis material may also be utilized, wherein a center layer is formed ofethylene-vinyl alcohol copolymer, layers adjacent to the center layerare formed of thermoplastic polyurethane, and outer layers are formed ofa regrind material of thermoplastic polyurethane and ethylene-vinylalcohol copolymer. Another suitable material for chamber 40 is aflexible microlayer membrane that includes alternating layers of a gasbarrier material and an elastomeric material, as disclosed in U.S. Pat.Nos. 6,082,025 and 6,127,026 to Bonk, et al. Additional suitablematerials are disclosed in U.S. Pat. Nos. 4,183,156 and 4,219,945 toRudy. Further suitable materials include thermoplastic films containinga crystalline material, as disclosed in U.S. Pat. Nos. 4,936,029 and5,042,176 to Rudy, and polyurethane including a polyester polyol, asdisclosed in U.S. Pat. Nos. 6,013,340; 6,203,868; and 6,321,465 to Bonk,et al.

Design Process

An alternate chamber configuration is depicted in FIG. 9 as chamber 40′.An exterior of chamber 40′ is formed from a polymer material thatprovides a sealed barrier for enclosing a fluid. The polymer materialdefines an upper surface 41′, an opposite lower surface 42′, and asidewall surface 43′ that extends around a periphery of chamber 40′ andbetween surfaces 41′ and 42′. In comparison with chamber 40, interiorbonds 45 are absent from chamber 40′, thereby imparting a smooth aspectto surfaces 41′ and 42′ due to the lack of indentations associated withinterior bonds 45. As with chamber 40, chamber 40′ tapers between heeland forefoot regions, incorporates differences in elevation in areas ofupper surface 41′, provides an indentation in the heel region and aprotrusion in the midfoot region, and has a generally planarconfiguration in the forefoot region. Accordingly, with the exception ofthe absence of interior bonds 45 and the indentations associated withinterior bonds 45, the shape of chamber 40′ is substantially identicalto chamber 40.

A further difference between chambers 40 and 40′ relates to fluidpressures. More particularly, the fluid pressure that may be containedwithin chamber 40′ is substantially reduced in comparison with chamber40. As the pressure within chamber 40′ increases beyond thirty-fivekilopascals (i.e., approximately five pounds per square inch), forexample, chamber 40′ may begin to expand outward or otherwise distendbecause interior bonds 45 are absent and do not restrict the expansion.More particularly, relatively moderate to high pressures in chamber 40′may cause surfaces 41′ and 42′ to distend outward until chamber 40′takes on a generally cylindrical or bulbous shape. The absence ofinterior bonds 45 effectively limits, therefore, the fluid pressurewithin chamber 40′ to relatively low levels. The absence of interiorbonds 45 may also permit changes in the shape of chamber 40′ during use.For example, a compressive force upon the heel region of chamber 40′ mayincrease the overall fluid pressure within chamber 40′, thereby inducingthe forefoot region of chamber 40′ to expand or distend outward.Accordingly, chamber 40′ may exhibit a decreased resistance todeformation during use when interior bonds 45 are absent.

In applications where the fluid pressure may be relatively low, chamber40′ may be utilized in footwear 10. In applications where a relativelyhigh fluid pressure may be beneficial, however, chamber 40 is utilizedin footwear 10 because interior bonds 45 and the elliptically-shapedstructures prevent surfaces 41 and 42 from expanding outward orotherwise distending significantly due to the pressure of the fluid.Through application of the design process discussed below, chamber 40′may be modified through the addition of interior bonds 45 in order toform chamber 40. That is, the design considerations discussed below maybe utilized to (a) modify the shape of chamber 40′, which may only beutilized with relatively low fluid pressures, and (b) arrive at theshape of chamber 40, which includes interior bonds 45, theelliptically-shaped structures that permit relatively moderate to highfluid pressures, and contouring to complement the general anatomicalstructure of the foot.

A first step in the design process for chamber 40 is to determine thepositions of interior bonds 45. Referring to FIG. 10, a top plan view ofchamber 40′ is shown as including a plurality of points 45′ that aredistributed to form a hexagonal array. Although a triangular array, asquare array, a rectangular array, or an irregular distribution may beutilized for interior bonds 45, an advantage to utilizing a hexagonalarray is that a distance between adjacent interior bonds 45 is moreregular than with other types of arrays. That is, a hexagonal arrayexhibits more uniform spacing than other types of arrays. Although thehexagonal array may be shifted in any direction or rotated, one ofpoints 45′ is depicted as being generally located at a center of theheel region of chamber 40′ and some of adjacent points 45′ are alignedto extend in the medial-lateral direction.

Another consideration relating to determining the positions of interiorbonds 45 is the spacing between adjacent interior bonds 45. Although thespacing between interior bonds 45 may vary significantly, the spacinghas an effect upon the stability of the elliptically-shaped structuresupon inflation. More particularly, the elliptically-shaped structuresmay be most stable when interior bonds 45 are spaced from each othersuch that the thickness in a majority of chamber 40 is greater than orequal to the distance between edges of the adjacent interior bonds 45,as discussed above. Although interior bonds 45 may have any shape andwidth, assume for purposes of an example that interior bonds 45 have acircular shape with a five millimeter diameter. Also assume that theminimum thickness of chamber 40′ is ten millimeters in areas that arenot immediately adjacent the edges of chamber 40′, where the thicknesseffectively drops to zero. In this example, the spacing between adjacentpoints 45′ should be at most fifteen millimeters because the distancebetween edges of the resulting interior bonds 45 will be tenmillimeters. That is, spacing points 45′ at a distance that is the sumof (a) the thickness of the minimum thickness of chamber 40′ and (b) tworadii of interior bonds 45 will impart the elliptically-shapedstructures with a width that is equal to or less than the thickness.Accordingly, through strategic planning when determining the positionsof points 45′, the resulting distance between edges of adjacent interiorbonds 45 may be equal to or less than the thickness in a majority ofchamber 40′, thereby imparting relatively high stability to theelliptically-shaped structures upon pressurization. In someconfigurations, however, advantages may arise if the distance betweenedges of adjacent interior bonds 45 is greater than the thickness ofchamber 40′. That is, the elliptically-shaped structures may have agreater width than height in some configurations.

Once the positions of points 45′ (i.e., the positions of interior bonds45) are determined, a second step in the design process for chamber 40is to determine the vertical position and angle of interior bonds 45. Inmanufacturing chamber 40, as described in greater detail below, polymersheets are heated, shaped, and bonded in various locations. In shapingthe polymer sheets, the sheets are drawn into the areas of interiorbonds 45. By properly positioning and angling interior bonds 45, changesin the thickness of the polymer sheets may be controlled such that eachof the polymer sheets and different areas of the polymer sheets haveoptimized thicknesses. Accordingly, properly determining the verticalpositions and angles for each of interior bonds 45 contributes toensuring that the polymer material of chamber 40 has a suitablethickness in each area of chamber 40. Referring to FIG. 5A, interiorbonds 45 located adjacent peripheral bond 44 are angled relative to ahorizontal plane, and interior bonds 45 located in a center of chamber40 are generally parallel to the horizontal plane.

Although interior bonds 45 may be located closer to one of upper surface41 and lower surface 42, interior bonds 45 are generally centeredbetween surfaces 41 and 42. Centering interior bonds 45 between surfaces41 and 42 contributes to ensuring that the degree to which (a) thepolymer material forming upper surface 41 is drawn downward and (b) thepolymer material forming lower surface 42 is drawn upward aresubstantially equal. That is, the amount of stretching in the polymermaterial is substantially equal when interior bonds 45 are locatedequally between surfaces 41 and 42. In some configurations,substantially equal stretching of the polymer materials forming uppersurface 41 and lower surface 42 may contribute to optimizing thethickness in each area of chamber 40. Referring to FIGS. 5A-5D, thevarious interior bonds 45 are generally centered between surfaces 41 and42.

The angle of interior bonds 45 is generally an average of the slope ofsurfaces 41 and 42. Referring to FIG. 11A, a cross-section throughchamber 40′ in the heel region is depicted. For purposes of reference, aline 46′ extends through chamber 40′ in a position of one of points 45′(i.e., in a position where one of interior bonds 45 will be formed). Aunit vector 47′ is depicted at each of surfaces 41′ and 42′ as extendingoutward in a perpendicular direction from surfaces 41′ and 42′. That is,unit vectors 47′ are normal to surfaces 41′ and 42′. Referring to FIG.11B, unit vectors 47′ are shifted to an area that is centered betweensurfaces 41′ and 42′, and a resulting vector 48′ is shown as being theaverage of the two unit vectors 47′. That is, unit vectors 47′ areaveraged to determine the directions associated with resulting vector48′. The angle of the interior bond 45 at this position is thencalculated as being normal to resulting vector 48′ and is depicted inFIG. 11B as line 49′. As an alternative to this process, the slopes ofsurfaces 41′ and 42′ may be determined at each location where line 46′intersects surfaces 41′ and 42′, and an average of the slopes may beutilized to determine the slope or angle of the interior bond 45 at thislocation.

Once the angles of all interior bonds 45 are determined utilizing thegeneral process discussed above, a third step in the design process forchamber 40 is to determine the shapes of surfaces 41 and 42. Moreparticularly, the third step involves the design of theelliptically-shaped structures between the adjacent interior bonds 45.Referring to FIG. 11C, various arcs 50′ extend upward and downward fromline 49′ to define the shape of portions of the elliptically-shapedstructures. When combined with similar arcs 50′ from adjacent bonds 45,the configurations of the various elliptically-shaped structures aredefined.

As a fourth step in the design process for chamber 40, differences inthe manner that various areas of chamber 40 will expand or otherwisedistend upon inflation may be accounted for. Referring to the forefootregion of FIG. 10, various points 51′ and 52′ are defined. While each ofpoints 51′ and 52′ are centered between adjacent points 45′, points 51′are closer to the adjacent points 45′ than points 52′. That is, points51′ are centered between two adjacent points 45′, whereas points 52′ arecentered between three adjacent points 45′. Upon pressurization, thepolymer material of chamber 40 will expand or otherwise distend outward,and the greatest expansion will occur in areas that are furthest frominterior bonds 45. That is, the areas in chamber 40 corresponding withpoints 52′ will experience greater expansion than the areas in chamber40 corresponding with points 51′. In order to account for thesedifferences in expansion, the design process may include adjustments tothe relative elevations of areas corresponding with points 52′. That is,the areas corresponding with points 52′ on upper surface 41 may beformed to have a lower elevation (e.g., one-third to one millimeter)than the areas corresponding with points 51′, and the areascorresponding with points 52′ on lower surface 42 may be formed to havea higher elevation (e.g., one-third to one millimeter) than the areascorresponding with points 51′. Upon pressurization of chamber 40,therefore, the areas corresponding with points 52′ will expand outwardto have an elevation that corresponds with points 51′, thereby formingmore uniform surfaces in chamber 40.

The design process discussed above, begins with an idealized chamberconfiguration (i.e., chamber 40′), which may not be suitable forrelatively moderate to high fluid pressures. Following various stepsthat include (a) laying out an array of points, (b) determining thevertical position and angle of interior bonds 45, (c) shaping surfaces41 and 42 to have the elliptically-shaped structures, and (d) adjustingthe shape to account for differences in expansion, chamber 40 is formedto have a configuration that may be more suitable for relativelymoderate to high fluid pressures.

Although the design process discussed above may be performed throughmanual calculations, a computer program may also be written or modifiedto perform the design process. For example, the shape of chamber 40′ maybe input into the computer program by the individual, and all othercalculations may be performed by the program, including determiningpositions for points 45′, the angles of bonds 45, the shapes of theelliptically-shaped structures, and adjustments to ensure equalelevations for points corresponding with points 51′ and 52′.

Manufacturing Method

A thermoforming process may be utilized to manufacture chamber 40. Asnoted above, the thermoforming process forms chamber 40 from a pair ofpolymer sheets that are molded and bonded to define surfaces 41-43. Moreparticularly, the thermoforming process (a) imparts shape to one of thepolymer sheets in order to form upper surface 41 and an upper portion ofsidewall surface 43 (b) imparts shape to the other of the polymer sheetsin order to form lower surface 42 and a lower portion of sidewallsurface 43, (c) forms peripheral bond 44 to join a periphery of thepolymer sheets, and (d) forms interior bonds 45 to join interiorportions of the polymer sheets between surfaces 41 and 42.

Utilizing the configuration of chamber 40 that is designed from theidealized shape of chamber 40′ and with the design process discussedabove, a mold 60 having an upper mold portion 61 and a lower moldportion 62 may be formed to have the configuration depicted in FIG. 12.Each of mold portions 61 and 62 cooperatively define an internal cavity63 with the configuration of chamber 40. When mold portions 61 and 62are joined together, therefore, cavity 63 has dimensions substantiallyequal to the exterior dimensions of chamber 40 in the unpressurizedstate. In other configurations, mold portions 61 and 62 maycooperatively define two internal cavities 63, one having theconfiguration of chamber 40, which is suitable for footwear 10 whenconfigured for the right foot of the individual, and the other havingthe configuration of a mirror image of chamber 40, which is suitable forfootwear 10 when configured for the left foot of the individual.

The manner in which mold 60 is utilized to form chamber 40 from twopolymer sheets 71 and 72 will now be discussed in greater detail.Initially, polymer sheets 71 and 72 are positioned between mold portions61 and 62, as depicted in FIG. 13A. A plurality of conduits may extendthrough mold 60 in order to channel a heated liquid, such as water oroil, through mold 60, thereby raising the overall temperature of mold60. When polymer sheets 71 and 72 are positioned within mold 60, asdescribed in greater detail below, heat may be transferred from mold 60to polymer sheets 71 and 72 in order to raise the temperature of polymersheets 71 and 72. At elevated temperatures that depend upon the specificpolymer material utilized, polymer sheets 71 and 72 soften or becomemore deformable, which facilitates shaping and bonding. In somemanufacturing processes, various conductive or radiative heaters may beutilized to heat polymer sheets 71 and 72 prior to placement within mold60 in order to decrease manufacturing times. The temperature of mold 60may vary depending upon the specific materials utilized for polymersheets 71 and 72.

Polymer sheets 71 and 72 respectively form upper surface 41 and lowersurface 42 of chamber 40. In addition, polymer sheets 71 and 72 eachform portions of sidewall surface 43. The thickness of polymer sheets 71and 72 prior to molding may be greater than the thickness of surfaces41-43 in chamber 40. The rationale for the difference in thicknessbetween polymer sheets 71 and 72 and surfaces 41-43 is that polymersheets 71 and 72 may stretch during the thermoforming process. That is,the thickness differences compensate for thinning in polymer sheets 71and 72 that occurs when polymer sheets 71 and 72 are stretched orotherwise deformed during the formation of upper surface 41, lowersurface 42, and sidewall surface 43.

Once polymer sheets 71 and 72 are positioned between mold portions 61and 62, mold portions 61 and 62 translate toward each other such thatpolymer sheets 71 and 72 enter cavities 63 and are shaped and bonded, asdepicted in FIG. 13B. As mold 60 contacts and compresses portions ofpolymer sheets 71 and 72, a fluid, such as air, having a positivepressure in comparison with ambient air may be injected between polymersheets 71 and 72 to induce polymer sheets 71 and 72 to respectivelycontact and conform to the contours of mold portions 61 and 62. Air mayalso be removed from the area between polymer sheets 71 and 72 and moldportions 61 and 62 through various vents, thereby drawing polymer sheets71 and 72 onto the surfaces of mold portions 61 and 62. That is, atleast a partial vacuum may be formed between polymer sheets 71 and 72and the surfaces of mold portions 61 and 62. As the area between polymersheets 71 and 72 is pressurized and air is removed from the area betweenmold 60 and polymer sheets 71 and 72, polymer sheets 71 and 72 conformto the shape of mold 60. More specifically, polymer sheets 71 and 72stretch, bend, or otherwise conform to extend along the surfaces ofcavities 63 within mold 60 and form the general shape of chamber 40. Inaddition to shaping polymer sheets 71 and 72, mold portions 61 and 62compress polymer sheets 71 and 72 together at locations correspondingwith peripheral bond 44 and interior bonds 45.

Once chamber 40 is formed within mold 60, mold portions 61 and 62separate such that chamber 40 and peripheral portions of polymer sheets71 and 72 may be removed from mold 60, as depicted in FIGS. 13C and 14.Chamber 40 is then permitted to cool, and a pressurized fluid may beinjected in a conventional manner. Referring to FIG. 12, mold portions61 and 62 are depicted as each including a channel 64 extending fromareas forming cavity 63. During the thermoforming process discussedabove, channels 64 form a conduit 73 that leads to chamber 40. Conduit73 may be utilized to inject the pressurized fluid, and conduit 73 maythen be sealed at a position that corresponds with peripheral bond 44 toseal chamber 40. In addition, excess portions of polymer layers 71 and72 may be trimmed or otherwise removed from chamber 40. The excessportions may then be recycled or reutilized to form additional polymerlayers 71 and 72 for other chambers 40.

Although the thermoforming process discussed above is a suitable mannerof forming chamber 40, a blowmolding process may also be utilized. Ingeneral, a suitable blowmolding process involves positioning a parisonbetween a pair of mold portions, such as mold portions 61 and 62. Theparison is a generally hollow and tubular structure of molten polymermaterial. In forming the parison, the molten polymer material isextruded from a die. The wall thickness of the parison may besubstantially constant, or may vary around the perimeter of the parison.Accordingly, a cross-sectional view of the parison may exhibit areas ofdiffering wall thickness. Suitable materials for the parison includemany of the materials discussed above with respect to chamber 40.Following placement of the parison between the mold portions, the moldportions close upon the parison and pressurized air within the parisoninduces the liquefied elastomeric material to contact the surfaces ofthe mold. In addition, closing of the mold portions and the introductionof pressurized air induces the liquefied elastomeric material to contactthe surfaces of the mold portions. Air may also be evacuated from thearea between the parison and the mold portions to further facilitatemolding and bonding. Accordingly, chamber 40 may also be formed througha blowmolding process. As a further alternative, a conventionalrotational molding process may be utilized for form chamber 40.

Further Configurations

Chamber 40, as discussed above and in the figures, has a configurationthat is suitable for a variety of footwear types and athleticactivities. In further configurations, chamber 40 may exhibit greaterthickness adjacent medial side than lateral side 14. The typical motionof the foot during running proceeds as follows: First, the heel strikesthe ground, followed by the ball of the foot. As the heel leaves theground, the foot rolls forward so that the toes make contact, andfinally the entire foot leaves the ground to begin another cycle. Duringthe time that the foot is in contact with the ground and rollingforward, it also rolls from the outside or lateral side to the inside ormedial side, a process called pronation. By providing greater thicknessto medial side 15, the rolling motion of the foot may be limited tocontrol pronation.

When incorporated into footwear 10, chamber 40 has a shape that fitswithin a perimeter of midsole 31 and extends from forefoot region 11 toheel region 13 and also from lateral side 14 to medial side 15, therebycorresponding with a general outline of the foot. Although thisconfiguration of chamber 40 is suitable for many footwear types, chamber40 may have a configuration that only extends under portions of thefoot. With reference to FIG. 15A, a version of chamber 40 that isintended to be located primarily in heel region 13 is depicted.Similarly, a version of chamber 40 that is intended to be locatedprimarily in forefoot region 11 is depicted in FIG. 15B.

Interior bonds 45 are depicted as being arranged in a hexagonal array.As noted above, however, interior bonds 45 may also be arranged in atriangular array, a square array, a rectangular array, or in anirregular distribution. With reference to FIG. 15C, a version of chamber40 wherein interior bonds 45 are arranged in a square array is depicted.Similarly, a version of chamber 40 wherein interior bonds 45 arerandomly distributed is depicted in FIG. 15D.

Chamber 40 has a configuration wherein the fluid within chamber 40 isfree to flow between regions 11-13 and is at one pressure. In anotherconfiguration, as depicted in FIG. 15E, a bond 53 extends across chamber40 and between sides 14 and 15. Bond 53 effectively segregates chamber40 into two subchambers that may each enclose a fluid with differentpressures. More particularly, bond 53 extends diagonally across heelregion 13 to provide a different fluid pressure in the rear-lateral areaof chamber 40. In some configurations, a bond similar to bond 53 mayextend from forefoot region 11 to heel region 13 in order to providedifferent fluid pressures in areas of chamber 40 corresponding withsides 14 and 15.

The invention is disclosed above and in the accompanying drawings withreference to a variety of embodiments. The purpose served by thedisclosure, however, is to provide an example of the various featuresand concepts related to the invention, not to limit the scope of theinvention. One skilled in the relevant art will recognize that numerousvariations and modifications may be made to the embodiments describedabove without departing from the scope of the present invention, asdefined by the appended claims.

1. An article of footwear having an upper and a sole structure thatincludes a fluid-filled chamber, the chamber comprising: a polymermaterial that defines a first surface, a second surface located oppositethe first surface, and a sidewall surface extending around a peripheryof the chamber and between the first surface and the second surface; anda plurality of bonds spaced inward from the sidewall surface and joiningthe first surface and the second surface, the bonds being distributed toform a regularly-spaced array, wherein the first surface and the secondsurface define elliptically-shaped structures between the bonds, theelliptically-shaped structures being in fluid-communication with eachother.
 2. The article of footwear recited in claim 1, wherein the arrayis hexagonal.
 3. The article of footwear recited in claim 1, wherein thechamber has a first thickness in a forefoot region and a secondthickness in a heel region, the first thickness being less than thesecond thickness.
 4. The article of footwear recited in claim 3, whereinthe elliptically-shaped structures have a first eccentricity in theforefoot region and a second eccentricity in the heel region, the firsteccentricity being less than the second eccentricity.
 5. The article offootwear recited in claim 3, wherein the first surface is oriented to beabove the second surface in the article of footwear, and an elevation ofthe first surface in the heel region is above an elevation of the firstsurface in the forefoot region.
 6. The article of footwear recited inclaim 5, wherein an elevation of the second surface in the heel regionis above an elevation of the second surface in the forefoot region. 7.The article of footwear recited in claim 1, wherein a majority of theelliptically-shaped structures have a width that is less than a length,the width being defined as a dimension extending between the bonds, andthe length being defined as a dimension that is perpendicular to thewidth.
 8. The article of footwear recited in claim 1, wherein a portionof the bonds are angled with respect to each other.
 9. The article offootwear recited in claim 1, wherein the bonds located adjacent aperiphery of a heel region of the chamber are angled with respect to ahorizontal direction, and the bonds located in a central area of theheel region are substantially parallel to the horizontal direction. 10.The article of footwear recited in claim 1, wherein a midfoot region ofthe chamber has a first thickness adjacent a medial side of the chamberand a second thickness adjacent a lateral side of the chamber, the firstthickness being greater than the second thickness.
 11. An article offootwear having an upper and a sole structure that includes afluid-filled chamber, the chamber comprising: a polymer material thatdefines a first surface, a second surface located opposite the firstsurface, and a sidewall surface extending around a periphery of thechamber and between the first surface and the second surface; and aplurality of separate bonds spaced inward from the sidewall surface andjoining the first surface and the second surface, the bonds beingdistributed to form a hexagonal array, and the bonds being located at amidpoint between the first surface and the second surface, wherein thefirst surface and the second surface define elliptically-shapedstructures between the bonds, the elliptically-shaped structures havinga first eccentricity in a forefoot region of the chamber and a secondeccentricity in a heel region of the chamber, the first eccentricitybeing less than the second eccentricity.
 12. The article of footwearrecited in claim 11, wherein the chamber has a first thickness in theforefoot region and a second thickness in the heel region, the firstthickness being less than the second thickness.
 13. The article offootwear recited in claim 11, wherein the first surface is oriented tobe above the second surface in the article of footwear, and an elevationof the first surface in the heel region is above an elevation of thefirst surface in the forefoot region.
 14. The article of footwearrecited in claim 13, wherein an elevation of the second surface in theheel region is above an elevation of the second surface in the forefootregion.
 15. The article of footwear recited in claim 11, wherein amajority of the elliptically-shaped structures have a width that is lessthan a length, the width being defined as a dimension extending betweenthe bonds, and the length being defined as a dimension that isperpendicular to the width.
 16. The article of footwear recited in claim11, wherein a portion of the bonds are angled with respect to eachother.
 17. The article of footwear recited in claim 11, wherein thebonds located adjacent a periphery of a heel region of the chamber areangled with respect to a horizontal direction, and the bonds located ina central area of the heel region are substantially parallel to thehorizontal direction.
 18. The article of footwear recited in claim 11,wherein a midfoot region of the chamber has a first thickness adjacent amedial side of the chamber and a second thickness adjacent a lateralside of the chamber, the first thickness being greater than the secondthickness.
 19. The article of footwear recited in claim 11, wherein thepolymer material is a thermoplastic polymer material.
 20. An article offootwear having an upper and a sole structure that includes afluid-filled chamber, the chamber comprising a polymer material thatdefines a first surface oriented to face the upper, an elevation of thefirst surface in a heel region of the footwear being above an elevationof the first surface in a forefoot region of the footwear; a secondsurface located opposite the first surface, an elevation of the secondsurface in the heel region of the footwear being above an elevation ofthe second surface in the forefoot region of the footwear; and aplurality of bonds that join the first surface and the second surface,the bonds being distributed to form a regularly-spaced hexagonal array.21. The article of footwear recited in claim 20, wherein the firstsurface defines a depression in the heel region.
 22. The article offootwear recited in claim 21, wherein the second surface has a planarconfiguration in the heel region.
 23. The article of footwear recited inclaim 22, wherein the bonds located adjacent a periphery of the heelregion are angled with respect to the bonds located in a central area ofthe heel region.
 24. The article of footwear recited in claim 20,wherein a midfoot region of the chamber has a first thickness adjacent amedial side of the chamber and a second thickness adjacent a lateralside of the chamber, the first thickness being greater than the secondthickness.
 25. The article of footwear recited in claim 20, wherein thechamber has a first thickness in the forefoot region and a secondthickness in the heel region, the first thickness being less than thesecond thickness.
 26. The article of footwear recited in claim 20,wherein the first surface and the second surface defineelliptically-shaped structures between the bonds.
 27. The article offootwear recited in claim 26, wherein the elliptically-shaped structureshave a first eccentricity in the forefoot region and a secondeccentricity in the heel region, the first eccentricity being less thanthe second eccentricity.
 28. The article of footwear recited in claim26, wherein a majority of the elliptically-shaped structures have awidth that is less than a length, the width being defined as a dimensionextending between the bonds, and the length being defined as a dimensionthat is perpendicular to the width.
 29. An article of footwear having anupper and a sole structure that includes a fluid-filled chamber, thechamber comprising: a polymer material that defines a first surface, asecond surface located below the first surface, and a sidewall surfaceextending around a periphery of the chamber and between the firstsurface and the second surface; a plurality of bonds spaced inward fromthe sidewall surface and joining the first surface and the secondsurface, the bonds being distributed to form a hexagonal array; and afluid located within the chamber, wherein the first surface has a firstpoint that is centered between two of the bonds that are adjacent toeach other, and the first surface has a second point that is centeredbetween three of the bonds that are adjacent to each other, the firstpoint being closer to the adjacent bonds than the second point, and thechamber having: an unpressurized state wherein the fluid has a pressuresubstantially equal to an ambient pressure surrounding the chamber, thefirst point being at a greater elevation than the second point when thechamber is in the unpressurized configuration; and an pressurized statewherein the fluid has a pressure greater than the ambient pressure, thefirst point being at an elevation of the second point when the chamberis in the pressurized configuration.
 30. The article of footwear recitedin claim 29, wherein the first surface and the second surface defineelliptically-shaped structures between the bonds.
 31. The article offootwear recited in claim 30, wherein the elliptically-shaped structureshave a first eccentricity in a forefoot region of the chamber and asecond eccentricity in a heel region of the chamber, the firsteccentricity being less than the second eccentricity.
 32. The article offootwear recited in claim 31, wherein the chamber has a first thicknessin the forefoot region and a second thickness in the heel region, thefirst thickness being less than the second thickness.
 33. The article offootwear recited in claim 30, wherein a majority of theelliptically-shaped structures have a width that is less than a length,the width being defined as a dimension extending between the bonds, andthe length being defined as a dimension that is perpendicular to thewidth.